This research project is analyzing properties of the buccopharyngeal component of swallowing and the effects of altering sensory and cortical inputs on the central pathway governing this reflex. Work in the young postnatally developing animal is attempting to define the receptive fields of sensory input which can alter the reflex and its threshold. A combined electrophysiological and electron micrographic study of the developing superior laryngeal nerve will also be undertaken to determine which fibers are essential to evoking swallowing and inhibiting respiration from the laryngeal region. The respiratory inhibition has a longer duration in the earliest postnatal stages and may present a model of study of the infant death syndrome. In the adult animal, work is continuing on the modification of the swallow by precentral cortex and peripheral sensory input. Modification of synaptic influences on single motoneurons are recorded indirectly by EMG recordings of discharge patterns of single motor units in specific cranial musculature. Regions of the precentral cortex integrating swallowing with mastication have been mapped, and this descending corticofungal affect on motor trigeminal and hypoglossal motoneurons is under study. Modification of sensory input affecting swallowing pathway includes the preparation of chronic animals with indwelling EMG electrodes which monitor single motor unit discharge patterning. Motor units are recorded in both normal cranial musculature and muscles with shortened tendon or severed tendons to alter sensory input during swallowing. The long-term alteration of musculature sensation in muscles active in swallowing is one of the approaches to determining methods of modifing the swallow and synaptic influences on its pathway.